Fortify Your Health: The Crucial Role of Sleep in Disease Prevention
Sleep is a natural, recurring state of rest, characterized by reduced consciousness, sensory activity, and voluntary muscle movement, during which the body undergoes restorative processes essential for physical and mental health.
It is as essential to life as food and water. It is a non-negotiable biological necessity.
Most people believe it is simply a time when our body and mind are dormant. On the contrary, sleep is an intricately coordinated physical dance. As you progress through various stages of sleep, the changes in brain activity are quite dramatic. In certain stages parts of the brain are up to 30% more active than when you are awake!
The Intricate Sleep Cycle
The sleep cycle involves 2 different phases and within one of these phases are 3 progressively deeper stages of sleep. The phases are classified as Non-REM (rapid eye movement) and REM. We cycle repeatedly through these phases about 4-6 times throughout the night, and we commonly awaken briefly between cycles. These cycles last on average about 90 minutes.
Non-REM sleep
Stage 1. The transition from being awake to a restful state.
Stage 2. Light sleep state. Your breathing, heart rate, and muscle movements slow down. Brain activity also slows, and body temperature drops.
Stage 3. Deep sleep state. Heart rate and breathing are the slowest during this phase, and one is not easily awakened. This stage is characterized by Delta brain waves. Events of the day are processed and memories are consolidated and filed securely in the brain. In this stage your body releases growth hormone, repairs muscle tissue and produces more cells to keep the immune system functioning well. The activity of the natural killer cells, the secret service agents of your immune system, particularly depend on optimal sleep.
A lack of time in this deep sleep stage can leave you feeling tired in the morning even if there was an adequate duration of total sleep.
REM Sleep
In this stage there are rapid horizontal eye movements. Brain activity rises as you breathe faster and your heart rate increases. During REM sleep you have the most vivid and hallucinogenic types of dreams. Just before you enter REM sleep, the brainstem sends a signal down the spinal cord to the muscles of your limbs to cause temporary paralysis so you do not act out the dreams. Insightful and highly creative thinking, and problem solving occurs during this time. Memories are processed and stored during REM sleep.
Chemical Messengers Orchestrating Our Sleep Cycle
Melatonin is the hormone released by the brain when it is dark and signals the cells that it is time to sleep. Sunlight or light exposure inhibits the release of melatonin and stimulates the release of cortisol, awakening us.
Serotonin, the body’s “feel good” chemical, is a neurotransmitter made by the brain. It is released during the day but at night it is used to make melatonin.
GABA is a neurotransmitter that inhibits nerve cell activity calming the body and allowing the body to sleep.
Adenosine is a neurotransmitter that slowly builds up in the brain during the day, and at high concentrations makes us drowsy at night. Caffeine works by blocking the brain receptors for adenosine keeping us alert.
Silent Dangers: The Link Between Sleep Deficiency and Disease
We all experience nights where we sleep poorly. But if sleep deprivation is prolonged and becomes chronic it is called sleep deficiency. Lack of good sleep does not simply make us irritable. It affects our learning, memory, immune system, mental health and even our DNA and genetic code. Sleep is an essential life sustaining process.
Sleep deficiency increases the risk of many chronic diseases including obesity, diabetes, cardiovascular disease, dementia and even early all-cause mortality.
Obesity: Several studies show that sleep deprivation, less than 7 hours a night increases the risk for obesity. A Nurses Health Study found an association between those who slept the least (5 hours or less a night) and those having the highest body mass index (BMI) and weight gain. (1)
The stomach releases a hormone that causes us to feel hungry (ghrelin) and fat cells release the hormone leptin that travels to the brain and causes us to feel full. Some studies suggest that sleep deprivation causes ghrelin levels to rise and leptin levels to drop. This may account for the association with obesity. Studies have shown multiple other mechanisms involved as well.Diabetes: Sleep deficiency (less than 7 hours) and longer sleep durations (more than 9 hours) have been shown in studies to increase the risk of diabetes mellitus. Metabolic changes such as higher cortisol levels leading to higher blood glucose is associated with chronic insufficient sleep. Clinical studies have found both increased glucose and insulin levels and reduced insulin sensitivity in sleep deficiency. (2)
Obstructive sleep apnea, a condition in which there is a blockage in the upper airway while sleeping, is associated both with obesity and sleep deficiency. This has been found to be an independent risk factor for insulin resistance.Cardiovascular disease: Both shorter and longer sleep durations are associated with cardiovascular disease, hypertension and strokes. This has been well documented in multiple studies.
People with Obstructive sleep apnea are also at increased risk for strokes, heart attack, and heart failure.
Depression: Poor sleep and insomnia (the inability to sleep or stay asleep) are associated with depression, especially when the insomnia becomes chronic. (3) Symptoms of extreme sadness and hopelessness can disrupt sleep as well. The National Institute of Mental Health findings show that insomnia as well as oversleeping are common signs of clinical depression.
Dementia: A recent study of nearly 8000 participants between the ages of 50 -70 years found that those who slept 6 hours or less a night showed a 30% higher risk of developing dementia in later life compared to those who slept 7 hours. (4)
Mortality: Chronic lack of sleep (less than 7 hours) and long sleep durations (more than 8 hours) are associated with a greater risk of all-cause mortality in a number of studies. Longer sleep times are associated with several factors linked to mortality including fatigue, stress, obstructive sleep apnea and coronary artery disease.
Sleep Challenges with Night Shift Workers
Shift Work Sleep Disorder (SWSD) is a condition that results from working atypical shifts, other than the typical 9 am to 5 pm schedule. This is a circadian rhythm sleep disorder that causes issues with falling asleep, staying asleep and sleepiness at unwanted times. It affects 10 to 40% of people who work nontraditional shifts for their jobs.
SWSD is associated with decreased alertness, higher risk of work-related accidents, and increased depression and anxiety. Metabolic changes increase the risk for heart disease, obesity, and digestive problems caused by irregular eating habits or poor diet.
Good sleep is not a luxury. It is your lifeline. Prioritize optimal sleep and you will unlock a world of health benefits that enhance every aspect of your life.
This is the first of a number of blogs on sleep…Yes. It is THAT important.
(1) Patel SR, Malhotra A, White DP, Gottlieb DJ, Hu FB. Association between reduced sleep and weight gain in women. American journal of epidemiology.2006 Nov 15;164(10):947-54.
(2) Grandner MA, Seixas A, Shetty S, Shenoy S. Sleep duration and diabetes risk: population trends and potential mechanisms. Current diabetes reports. 2016 Nov 1;16(11):106.
(3) Fernandez-Mendoza J, Shea S, Vgontzas AN, Calhoun SL, Liao D, Bixler EO. Insomnia and incident depression: role of objective sleep duration and natura lhistory. Journal of sleep research. 2015 Aug;24(4):390-8.
(4) Sabia S, Fayosse A, Dumurgier J, van Hees VT, Paquet C, Sommerlad A, Kivimäki M, Dugravot A, Singh-Manoux A. Association of sleep duration in middle and old age with incidence of dementia. Nature Communications. 2021 Apr 20;12(1):1-0.